The Temperatures of White Dwarfs in Accreting Binaries

Abstract

Long-term observations of the dwarf nova WZ Sge with an outburst recurrence time of 33 years are studied. The results indicate that the UV flux reached an equilibrium value at about the end of 1986; this means that the UV flux continued to decrease for 8 years after outburst. If the underlying dwarf has provided a dominant amount of the UV flux since the disk reached quiescence, then the outer layers of the white dwarf cooled by several thousand degrees. The indications are that a 13,500 K + or - 500 K white dwarf contributing most of the UV flux is consistent with the observed parameters of WZ Sge; however, there must be some contribution from the hot disk or a larger emitting area.